Leslie H. Hicks

Effects of Overtraining on Acquisition and Reversal of Place and Response Learning

Five groups of rats were given 0, 25, 50, 75, and 100 overtraining trials in a T-maze to determine the effects on the acquisition and reversal of place and response habits. Increasing overtraining produced more response than place learners, but there was no facilitative effect in reversal learning with increased overtraining, nor was there a differential effect on the ease of reversal of place or response learning.

Effects of caudate and cortical lesions on place and response learning in rats

Rats with lesions in the caudate nucleus made fewer errors and took fewer trials to reach criterion than unoperated rats in acquisition and reversal performance on a T-maze task. On place and response performance, caudate and cortical rats did not differ from unoperated rats in number of errors and trials to criterion. Caudate rats were predominantly place learners, while cortical rats were mainly response learners. The results are discussed in relation to compensatory behavioral mechanisms following brain lesions.

Lipreading in patients with schizophrenia.

This study was designed to explore whether schizophrenic patients who are able to maintain their gaze with adequate persistence could competently lip-read. Four lipreading tests, designed to assess recognition of syllables, words, and overlearned sentences, were administered to 15 schizophrenic and 15 normal subjects matched for age, sex, and educational level. The patients proved to be competent lip-readers susceptible to the blend illusion and were inferior only in lipreading of overlearned sentences. The latter difficulty may tentatively be attributed to the inadequacy of the patients premorbid social network for establishing contextual cues that aid in the recognition of overlearned sentences.

Glyconutrients and perception, cognition, and memory.

Neuropsychological tests were administered to 62 college students to assess the influence of glyconutrients on perception, cognition and memory in two randomized, double-blind, placebo-controlled, counterbalanced studies. Participants were given both a glyconutritional supplement and a control substance prior to testing. In Exp. 1, a Same-Different visual discrimination task, Ravens Standard Progressive Matrices, and the Stroop test were administered. In Exp. 2, simple and complex working-memory capacity were measured. Participants receiving the supplement performed significantly more accurately on the visual discrimination task and the first session of the simple working-memory test.

Startle eyeblink modulation: detecting changes in directed attentional allocation during early preattentive processing

Startle eyeblink modification was examined as a measure of allocation of attentional resources during active attention tasks in the early stage of information processing. Fifty-five participants were presented with a series of 250- and 40-ms tones of either high or low pitch which were followed by startle-eliciting stimuli at a lead interval of 120 ms. Attentional allocation was manipulated by instructing one group (Passive) to simply listen to the tones; the second group (Active 1) to count the number of low tones and the third group (Active 2) to count the long high-pitched tones and the short low-pitched tones. Startle eyeblink was significantly more inhibited for the Active 1 group than the Passive group (control) with no significant difference between the two directed attentional conditions (Active 1 and Active 2 groups). However, across the three attentional groups, the degree of startle eyeblink modulation appeared to reflect the degree of attention allocated to the task. The results support the utility of the startle probe in evaluating controlled attentional allocation during the early stages of information processing.

Effects of lesions in the basal ganglia on the retention of two-way active avoidance performance

The effects of lesions in the globus pallidus, substantia nigra, and the parafascicular nuclei of the thalamus on the retention of an active avoidance task were studied. The role of these basal ganglia and thalamic nuclei in the speed of initiating an avoidance response was assessed. Lesions of the substantia nigra and the globus pallidus severely hindered retention performance of a two-way active avoidance response. Parafascicular lesions impaired performance to a lesser degree.

Effects of stimulus rotation on discrimination learning by monkeys

Monkey performance on object and pattern discriminations was compared under various stimulus rotational conditions: (1) positive and negative stimuli remain constant, (2) only positive stimulus rotates, (3) only negative stimulus rotates, (4) both stimuli rotate. Performance was best at the condition in which only the negative stimulus rotated.

DISCRIMINATION OF FIGURAL ORIENTATION BY MONKEYS AND CHILDREN

The performance of 6 monkeys and 5 children was compared on a task involving the discrimination of changes in orientation of plane figures. Children made fewer errors than monkeys when figures were rotated 180°. For both groups the sequence of presentation of problems was an important determinant of performance.

The relative dominance of form and orientation in discrimination learning by monkeys and children

Eleven nursery school children and nine monkeys were trained to discriminate stimulus figures differing in form and orientation. On two of the four problems, children were superior in the learning of the discrimination. Test trials were given to determine the relative dominance of form and orientation. For both children and monkeys, form was selected significantly more often than orientation.

Denatonium Saccharide as an Aversive Stimulus in a Conditioned Taste Aversion Paradigm

The ability of denatonium saccharide (DS) to function as an aversive stimulus for the rat was studied in a conditioned taste-aversion paradigm in two experiments. Exp. 1 assessed the effects of DS during a 30-min. access period when only a saccharin solution was available. Exp. 2 assessed the effects of DS during both a 10-and a 30-min. access period when a saccharin solution and free water were available. The results showed that DS did not attenuate saccharin consumption reliably over all test days. The effect was most apparent during the 10-min. interval when free water was available. These results, together with previous reports, suggest that DS appears to function as a weak aversive stimulus in the rat.